Electromagnetic wave
A wave of oscillating electric and magnetic fields that travels through empty space at c = 3.00e8 m/s.
Last updated
Analogy
Two fields pushing each other along, needing no medium.
Example
lambda = c / f= 3e8 / 1e8= 3 m
In practice
A 100 MHz radio wave has a wavelength of 3 m.
Practice
Flashcards
- How fast do EM waves travel in a vacuum?About 3.00e8 m/s.
Questions people ask
How did Maxwell predict light?
Maxwell's equations showed that a changing electric field makes a magnetic field and vice versa. His equations gave a wave speed equal to 1 over the square root of mu0 epsilon0, which matched the measured speed of light. He concluded that light is an electromagnetic wave.
Do EM waves need a medium?
No. They are self-sustaining oscillations of electric and magnetic fields, so they travel through a vacuum. Sunlight crosses about 150 million kilometres of empty space to reach Earth. In materials such as glass or water, the waves slow down but keep going.